Quercetin is a flavonoid pigment found in many plants and foods such as apples and berries, onions, Ginkgo biloba, red wine, green tea, St. John’s wort, American elder and Buckwheat tea.
Quercetin has unique biological properties that may improve mental as well as physical performance and reduce risk of infection mainly upper respiratory tract ones (URTI). These properties extend to benefits to the overall health disease resistance including anti-carcinogenic, anti-inflammatory, antiviral, antioxidant and psychostimulant activities as well as the ability to inhibit lipid peroxidation, platelet aggregation and capillary permeability and to stimulate mitochondrial biogenesis.
The estimated absorption of quercetin glucoside; the naturally occurring form of quercetin, ranges from 3% to 17% in healthy individuals. This low bioavailability may be attributed to its low absorption, extensive metabolism and/or rapid elimination, hence, the need for special formulation that improves the pharmacokinetics especially the absorption and thus bioavailability of this product. The dose of quercetin widely assessed in human clinical studies varies between 500 and 1000 mg/day.
There are several studies in humans investigating the correlation of quercetin and its immunomodulatory effects. 1000mg/day Quercetin does indeed reduce illness (URTI) after intensive exercise like long time cycling. 1000 mg/day quercetin reduces post-exercise measures for both inflammation and oxidative stress and improves exercise performance compared to placebo. Also, 12 weeks of 1000mg/day of quercetin reduces URTI total sick days and severity by 31% and 36% (statistically significant) in 40 years-old and older subjects who rated themselves as physically fit.
On the mechanism of action, Quercetin was classified as a long lasting anti-inflammatory substance that possesses strong anti-inflammatory capacities on different human cells. Quercetin modulates the Th1 and Th2 cytokine production in favor of a reduced inflammatory response, inhibition of TNFα and poly (ADP-ribose) polymerase-1 in pulmonary epithelial cells [PARP-1] with preservation of cellular NAD1 and energy production in the lungs cells that helps the healing process.
Quercetin possesses strong anti-oxidant properties.
Quercetin has mitochondrial biogenesis properties leading to improved muscles performance and increase glucose uptake by muscles cells.
In vitro studies showed that quercetin could antagonize SARS-CoV entry into the host cells. SARS-CoV is the coronavirus that was behind the SARS epidemic in 2002.
In vitro studies have also demonstrated that quercetin acts as a potent antiviral agent by inhibiting viral replication of several respiratory viruses, including influenza virus, parainfluenza virus, respiratory syncytial virus (RSV), adenovirus and rhinovirus at various stages of their cell invasion.
Figure courtesy of Kinker B et al.
- Quercetin overview: webmd. https://www.webmd.com/vitamins/ai/ingredientmono-294/quercetin
- Yao Li et al. Review: Quercetin, Inflammation and Immunity. Nutrients 2016, 8, 167; doi:10.3390/nu8030167
- Nieman DC et al. Effects of quercetin and EGCG on mitochondrial biogenesis and immunity. Med Sci Sports Exerc. 2009 Jul;41(7):1467-75
- Nieman DC et al. Quercetin’s influence on exercise performance and muscle mitochondrial biogenesis. Med Sci Sports Exerc. 2010 Feb;42(2):338-45
- Heinz SA et al. Quercetin supplementation and upper respiratory tract infection: A randomized community clinical trial. Pharmacol Res. 2010 Sep;62(3):237-42
- Somerville V et al. Effect of Flavonoids on Upper Respiratory Tract Infections and Immune Function: A Systematic Review and Meta-Analysis. Adv Nutr 2016;7:488–97
- Ling Yi et al. Small Molecules Blocking the Entry of Severe Acute Respiratory Syndrome Coronavirus into Host Cells. JOURNAL OF VIROLOGY, Oct. 2004, p. 11334–11339
- Kinker B et al. Quercetin: A Promising Treatment for the Common Cold. J Anc Dis Prev Rem 2014, 2:2 DOI: 10.4172/2329-8731.1000111
Beta-glucans are found in baker’s yeast. They are naturally occurring polysaccharides. These glucose polymers are constituents of the cell wall of certain pathogenic bacteria and fungi. They are considered powerful immuno-modulators.
Beta-glucans increase host immune defense by activating complement system and enhancing macrophages and natural killer cell function. Their immunity boosting effects involve their specific interaction with several cell surface receptors, as complement receptor 3 (CR3; CD11b/CD18), lactosylceramide, selected scavenger receptors, and dectin-1 (betaGR)
Beta Glucan has been shown to be effective in preventing upper respiratory viral infections (URTI-colds and the flu) in several double-blind studies. Also, it lowers the severity of influenza infection and mortality in animal studies.
Beta-glucans contribute to the maintenance of normal blood cholesterol levels. This presumably help in decreasing atherosclerosis and cardiovascular disease.
Consumption of betaglucans from oats or barley as part of a meal contributes to the reduction of the blood glucose rise after that meal.
While the dose for boosting immunity and preventing URTI ranges between 100 and 500 mg per day, the EU Register on nutrition and health claims authorizes the claims on decreasing cholesterol and regulating glucose for meals that provide doses between 1 and 4 g (1000-4000 mg) of beta-glucans from oat meals.
- Jesenak M et al. Respiratory Tract Infections and the Role of Biologically Active Polysaccharides in Their Management and Prevention. Nutrients 2017, 9, 779; doi:10.3390/nu9070779
- Akramiene D et al. Effects of beta-glucans on the immune system. Medicina (Kaunas). 2007;43(8):597-606
- Shawn Talbott and Julie Talbott. Effect of BETA 1, 3/1, 6 GLUCAN on upper respiratory tract infection symptoms and mood state in marathon athletes. Journal of Sports Science and Medicine (2009) 8, 509-515
- Tanita Dharsono, Karolina Rudnicka, Manfred Wilhelm & Christiane Schoen. Effects of Yeast (1,3)-(1,6)-Beta-Glucan on Severity of Upper Respiratory Tract Infections: A Double-Blind, Randomized, Placebo-Controlled Study in Healthy Subjects. Journal of the American College of Nutrition 2019, Vol. 38, No. 1, 40–50
- EU Register on nutrition and health claims
Elderberry has been used in folk medicine for centuries to treat influenza, colds and sinusitis. It has also been reported to have antiviral activity against influenza and herpes simplex. 300 mg of Elderberry has shown a significant reduction of common cold duration and severity in air travelers. One study of 60 people with influenza found that those who took 60 mg of elderberry syrup showed symptom improvement in two to four days of their symptoms, while the control group took seven to eight days to improve. A good dose would be between 60-300 mg/day. Since natural elderberry contain cyanide, supplements preparation should be void of this lethal component. Indeed, there are 3 mg of cyanide per 100 grams of fresh berries and 3–17 mg per 100 grams of fresh leaves. This is just 3% of the estimated fatal dose for a 130-pound (60-kg) person. Quality check of production should be exerted.
- Tiralongo E et al. Elderberry Supplementation Reduces Cold Duration and Symptoms in Air-Travellers: A Randomized, Double-Blind Placebo-Controlled Clinical Trial. Nutrients 2016, 8, 182; doi:10.3390/nu8040182
- Zakay-Rones Z, Thom E, Wollan T, Wadstein J. Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections. J Int Med Res. 2004 Mar-Apr;32(2):132-40